Quiz: Rerooting Transition

Rerooting: You computed sum of distances from node $1$. Now you move the root from $u$ to its child $v$. Subtree of $v$ has $s$ nodes, tree has $n$ total. How does the sum change?

1. A.Changes by $n - 2s$
2. B.Decreases by $s$
3. C.Stays the same
4. D.Increases by $s$